[DebugInfo] Simplify and speedup .debug_aranges parsing

Parsing .debug_aranges section now takes O(nlogn) operations instead
of O(n^2), where "n" is the number of address ranges. With this change,
the time required to symbolize an address from a random large
Clang-generated binary drops from 165 seconds to 1.5 seconds.

No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191781 91177308-0d34-0410-b5e6-96231b3b80d8